<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=yes" />
    <title>ShellCheck: SC2313 – Quote array indices to avoid them expanding as globs.</title>
    <link rel="stylesheet" href="css/bootstrap.min.css" />
  </head>
  <body style="margin-left: auto; margin-right: auto; max-width: 800px">
    <h1>SC2313 – ShellCheck Wiki</h1>
    <a href="https://github.com/koalaman/shellcheck/wiki/SC2313">See this page on GitHub</a>
    <p style="display: none"><a href="index.html">Sitemap</a></p>
    <hr />
    <h2 id="quote-array-indices-to-avoid-them-expanding-as-globs">Quote
array indices to avoid them expanding as globs.</h2>
<h3 id="problematic-code">Problematic code:</h3>
<div class="sourceCode" id="cb1"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb1-1"><a href="SC2313.html#cb1-1" aria-hidden="true" tabindex="-1"></a><span class="bu">read</span> <span class="at">-r</span> <span class="va">foo[</span>index<span class="op">]</span></span></code></pre></div>
<h3 id="correct-code">Correct code:</h3>
<div class="sourceCode" id="cb2"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb2-1"><a href="SC2313.html#cb2-1" aria-hidden="true" tabindex="-1"></a><span class="bu">read</span> <span class="at">-r</span> <span class="st">&quot;foo[index]&quot;</span></span></code></pre></div>
<h3 id="rationale">Rationale:</h3>
<p>ShellCheck found an array element passed to read, where the
<code>[]</code> was not quoted. This means the array index
<code>[index]</code> will be treated as a glob range, and the word may
be replaced or trigger <code>failglob</code>.</p>
<p>In the problematic example, having a directory named
<code>food</code> will cause the command to become
<code>read -r food</code> instead, since <code>food</code> matches the
glob <code>foo[index]</code>. The result is assigning a value to the
wrong variable.</p>
<p>Quote or escape the pattern as shown to ensure it always reads into
the array <code>foo</code> at index <code>index</code>.</p>
<h3 id="exceptions">Exceptions:</h3>
<p>None.</p>
<h3 id="related-resources">Related resources:</h3>
<ul>
<li>Help by adding links to BashFAQ, StackOverflow, man pages, POSIX,
etc!</li>
</ul>
    <hr />
    <p style='font-size: 80%'><a href="../index.html">ShellCheck</a> is a static analysis tool for shell scripts. This page is part of its documentation.</p>
  </body>
</html>


